So I'm new to modding GTA IV, but I think I got it figured out pretty much.
The only problem is, not matter what i try, i cant get rid of the taxi bug.
I'd like your opignion on what i might be doing wrong here.

I got GTA IV + EFLC from steam, I downgraded to patch 1.0.4.0
Then i got scripthook
Then i got the Dsound.dll
Then i got Xlive and Xlive_d
And I'm running Icenhancer v2.0 with settings by Jumper311

Then i started modding my cars, and ofc i also got the taxi bug.
So far I have tried:
- Traffic control
- Traffic flow
- Vehicle selector (buy a buttload of cars ao they are loaded in the memory, just makes my game lag and get texture problems)
- Taxi bug fix by Scigheras

You're not doing something wrong, GTA 4 is just stupid that way. I've tried countless times to get the amount of taxi's to an acceptable amount without performance taking any damage (with no luck).

The best thing you can do is turning the traffic density down to 20 (or lower). Then just install any of those fixes. I've had the most luck with traffic control (system) I think, might be a different one because I tried so many. You might also want to try one of those lightweight car packs (they usually come with a fix along with em). Keeping the size of your vehicles.img as low as possible certainly does seem to help a bit.